1. Field of the Invention
This invention relates to pneumatic tires, and more particularly to a heavy duty pneumatic radial tire for use in truck and bus use capable of reducing tire noise.
2. Description of Related Art
During the running of the tire, vibrations are applied to the tire due to local variation of rigidity in a tread pattern and unevenness of road surface, which vibrations propagate in air to cause noise. Such tire noise is closely related to resonance frequency of a tread or a sidewall portion, so that it is particularly effective to improve vibration properties of the sidewall portion for reducing noise in this type of the tire.
As regards the vibration properties of the sidewall portion, various countermeasures for reducing tire noise are proposed in tires for passenger cars, while no countermeasure for this type of tire noise is proposed in heavy duty pneumatic radial tires for use in truck and bus.